1. Field of the Invention
The present invention relates to a biochemical reaction cassette, a detection apparatus to be used for such a biochemical reaction cassette and a detection method for detecting a target substance caught by the probes of such a biochemical reaction cassette.
2. Description of the Related Art
Currently, massive research efforts are being paid in a short period of time to look into the polymorphism and the expression amount of genes in conjunction with the progress of the technology of analyzing genomic information. DNA micro-arrays are being popularly used as means for analyzing genomic information under the circumstances where genomic information is required to be analyzed with such a high degree of throughput. A DNA micro-array is prepared by highly densely immobilizing a large number of probes that can specifically be bound to a biomolecule such as DNA on a substrate such as a glass slide. Genes are extracted from a specimen such as blood taken from a subject, then amplified and labeled typically by a fluorescent dye. As the labeled genes are developed on a DNA micro-array by an appropriate means and the reaction conditions including the temperature are adjusted, a hybridization reaction takes place between the developed genes and the probes. When the specimen contains genes that can specifically be bound to the probes, they are bound to the corresponding probes. Since the genes are labeled in advance, it is possible to determine the type and the quantity of the genes contained in the specimen from the positions on the DNA micro-array where the labels emit a signal and the intensity of the signal.
Known specimen analyzing apparatus adapted to use a DNA micro-array include those for extracting genes from a specimen, those for amplifying the extracted genes and those for labeling genes with a fluorescent dye as well as those for developing the genes labeled by means of any of above listed apparatus and causing a hybridization reaction to take place and those for detecting the positions of fluorescent labels and the intensities of fluorescence on the DNA micro-array after the reaction. However, the operation of any of such apparatus is time consuming and cumbersome because the genes extracted from the specimen have to be moved from apparatus to apparatus by hand. Additionally, a huge space is required to install all such apparatus. Currently, such specimen analyzing apparatus are mostly for research applications. In other words, the time-consuming and cumbersome operation and the requirement for a large space may not raise a particular problem for the present. However, as the performance of DNA micro-arrays is improved in the near future, specimen analyzing apparatus of the type under consideration will find applications in the field of clinical practice for the purpose of examinations. Then, the time-consuming and cumbersome operation and the requirement for a large space will constitute a barrier against quick examinations.
A compact biochemical reaction cassette realized by integrally combining such apparatus other than a fluorescence detection apparatus has been developed to dissolve the problem of cumbersomeness operation and the requirement for a large space (Japanese Patent Application Laid-Open No. H10-505410). The DNA micro-array that is arranged in such a biochemical reaction cassette is downsized as compared with the micro-arrays arranged in known apparatus. To accurately detect signals of fluorescence by means of such a downsized DNA micro-array, the DNA micro-array has to be arranged in parallel with the detection surface of the detection apparatus and secured there. Then, a highly precise adjustment mechanism is required to accurately place the DNA micro-array in position. Additionally, in the analysis of genomic information that utilizes a specific binding of DNA, a denaturing process (of heating to a temperature level higher than the melting temperature Tm) for the purpose of reducing a double-stranded DNA to a single-stranded DNA and/or a hybridization reaction or some other reaction that needs to be conducted at high temperature are often required. Then, the biochemical reaction cassette itself can be deformed by heat applied to it. Thus, even if the DNA micro-array is successfully arranged in parallel with the detection surface of the detection apparatus and secured there initially, the plane of the DNA micro-array may not be kept in parallel with the detection surface of the detection apparatus. In such a case, it may not be able to accurately define the focal point of the detection apparatus. The net result will be that the operation of detecting signals of fluorescence may not reliably be conducted.
In view of the above-identified circumstances, it is therefore an object of the present invention to provide a method of using a biochemical reaction cassette comprising a DNA micro-array and keeping the plane of the DNA micro-array in parallel with the detection surface of a detection apparatus in order to make it possible to accurately detect a desired target substance such as genes by way of a simple operation. Another object of the present invention is to provide a biochemical reaction cassette and a detection apparatus to be used for such a biochemical reaction cassette to which the method of the present invention is applicable.
It may be needless to say that the scope of application of the present invention is by no means limited to DNA micro-arrays and the present invention can be applied to probe arrays where biomolecules of any of various types are arranged on a substrate as probes.